It’s the line-ups which continue to give the game away.
A bumper crowd of 40,492 at Stamford Bridge suggested a match of over-arching tradition and importance – a classic third round tie.
So did the evocative 1970 cup final replay kit the Blues wore – yellow socks and all - along with the half-time salute to the crowd from Chopper Harris and a few of his mates from that legendary era in the club’s history.
The fans cared. There was a great away following from Championship side Forest and the sort of low guttural chants and mickey-taking from the home fans which pointed to a match that mattered.
Then there was the retro programme cover – a beautifully simple design carrying echoes of FA Cup pasts. Another suggestion that this famous old competition still holds significance.
And in his programme notes, Frank Lampard talked a good game too – pointing out how much it means to him as a four times winner who grew up adoring the competition.
But oh, those line-ups. There is just no getting away from it. Clubs are cashing in on a well of nostalgia but they will not be able to do that indefinitely when under-strength sides are increasingly the norm.
With each passing year, the competition feels like a competition for the reserves.
The day before Chelsea’s 2-0 stroll over Forest, fewer than 13,000 showed up for Fulham’s battle with Premier League Aston Villa. There, simple nostalgia was not enough to swell the gate to old-school proportions, and the much-changed line-ups perhaps explained the reduced appeal.
Fulham boss head coach Scott Parker lamented the ‘loss of some sparkle’ in the famous old competition, citing the tampering with schedules, replays and cup final kick-off times. But he too left out his two star players as he attempts to navigate a path back to the Premier League.
It was the same at the Bridge, where many of the heavy hitters from both sides were rested.
In the 70s, Leeds manager Don Revie received widespread condemnation for resting players and not fielding the best XI in order to save them for other matches. Now, everyone is at it.
You would not say that Lampard fielded a team of unknown youths. Every one of his players has first-team experience. But in the starting line-up there was no Kepa, no Rudiger, no Mount, no Abraham, no Azpilicueta, no Alonso, no Kante, no Pulisic.
And Forest too were far from wholly committed, with head coach Sabri Lamouchi determined not to do anything which might undermine that all-important priority of making the play-offs.
The Blues were two up at the break and already cruising, so they will feel their changes were totally appropriate and well judged.
Forest may feel they missed a chance to claim a significant scalp. But then again, the management and players probably won’t care so much if they are not to be sucked deeper into the cup.
That is where we are now and it is not as if we are in need of a Greta Thunberg-style activist to alert any lingering FA Cup-change deniers to the reality. Fewer and fewer fans are under any illusions about the diminished status of this venerable old trophy.